Electromagnetic relay

Abstract

An electromagnetic relay adapted to be driven by a.c. voltage includes two windings formed by two wires wound together, each winding having its ends connected through diodes to a respective terminal of the a.c. voltage source. The diodes are connected to each terminal with opposite forward directions so that the magnetic fluxes generated by the two windings have the same direction irrespective of the polarity of the a.c. voltage. The capacity existing between the two windings acts as a reactance for limiting the exciting current without consuming active energy.

I claim: 
     
       1. An electromagnetic relay adapted to be driven from an a.c. voltage source, comprising (a) a coil having first and second electrically insulated, capacitively coupled windings,   (b) a first pair of diodes connected in opposite forward directions between the respective ends of said first winding and a first terminal of said a.c. voltage source, and a second pair of diodes connected in opposite forward directions between the respective ends of said second winding and a second terminal of said a.c. voltage source, so that the magnetic fluxes generated by said first and second windings have the same direction irrespective of the polarity of the a.c. voltage, and   (c) a contact system including at least one fixed contact and one movable contact adapted to be moved by said magnetic fluxes.   
     
     
       2. The relay of claim 1, wherein the a.c. voltage required to move said movable contact satisfies substantially the following equation: ##EQU2## wherein θ is the sum of said magnetic fluxes required to move said movable contact, w is the number of turns of each of said first and second windings,   ω is the angular frequency of said a.c. voltage,   C is the capacity between said first and second windings, and   R is the ohmic resistance of each of said first and second windings,   
     
     
       3. The relay of claim 2, wherein said first and second windings are formed by coiling two wires together, said capacity being constituted by the winding capacity between said wires. 
     
     
       4. The relay of claim 1, including means for protecting said first and second windings against surge voltages. 
     
     
       5. The relay of claim 4, wherein said protecting means includes a bipolar Zener diode connected between said first and second terminals. 
     
     
       6. The relay of claim 5, wherein said Zener diode and said first and second pairs of diodes are formed as a common unit.